Medical gear pump for suctioning and rinsing

ABSTRACT

A medical gear pump is used for suction and irrigation, in particular for endoscopy or the laboratory, and it has two meshing gears as conveying elements, one of which is joined to a drive mechanism. The gears are received in non-journal-mounted fashion in openings, and are each equipped with a helical tooth set. It is proposed to configure the helical tooth set such that, when viewed along a surface line of said gears, at least two tooth tip/root contact points of said meshing gears are present, and a contour of tooth spaces of the one gear is matched to the teeth of the other gear in such a way that when a tooth has completely penetrated into the tooth space, its tooth tip almost completely fills up the tooth space radially inside the pitch circle.

CROSSREFERENCE OF PENDING APPLICATION

This application is 371 of pending international applicationPCT/EP98/03601 filed on Jun. 15, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical gear pump for suction andirrigation, in particular for endoscopy or the laboratory, comprisingtwo meshing gears as conveying elements, one of which is joined to adrive mechanism, the gears being received in cylindrical openings of apump housing and the openings being connected to an inlet and to anoutlet, the gears being received in non-journal-mounted fashion in theopenings and the two gears each being equipped with a helical tooth set.

2. Related Prior Art

A gear pump of this kind for homogenizing medical, cosmetic, andtechnical products and mixtures is known from German Utility Model No.18 22 807.

It is possible for gears mounted in non-journal-mounted fashion to sealthemselves with respect to the housing wall during operation as a resultof the differential pressure of the pump.

In German Utility Model No. 18 22 807, coupling of the doublyball-bearing-mounted drive shaft to the directly drive gear isaccomplished by way of an oval stem end that is inserted into an ovalbore in the driven gear. This primarily serves the purpose of betteremulsification, since the eccentric freedom of movement of the directlydriven gear with respect to the drive shaft is one-dimensional andco-rotates. Consistent sealing, over the entire rotation, of the toothtips in the cylindrical bore in which the gears are received is therebyprevented, since because of its eccentricity, the directly driven gearis lifted to some extent out of its self-sealing position twice duringeach rotation. To ensure smooth operation, a mounting system for thepump drive shaft that is impact-damped using rubber rings is thereforeprovided.

A similar bearing system for the driven shaft is known from GermanUtility Model No. 18 21 554.

A gear pump of this kind for delivering highly aggressive media is knownfrom German Utility Model No. 19 75 041.

It is known from DE 83 31 598 U1 to additionally provide irrigationconduits.

When a pump of this kind is used in the medical field, the actualconveying means, i.e. the gears and the corresponding flow conduits,come into contact with the medical liquids, thus posing the problem ofcleaning and disinfection.

The pumps that have become established in the medical field aretherefore primarily peristaltic ones, in which the medical liquids aretransported by rollers which act externally on flexible tubes.

Although it is possible thereby to ensure that the actual conveyingelements do not come into direct contact with the medical liquid, theresulting conveyed flow is nevertheless a pulsating flow, which is notespecially suitable, in particular, for applications in hysteroscopy,urology, and arthroscopy.

It is therefore the object of the present invention to create a medicalpump which on the one hand is of simple design and also easy to clean,and moreover supplies a continuously variable controllable conveyed flowwith high pump efficiency.

SUMMARY OF THE INVENTION

According to the present invention, the object is achieved in that inthe case of the gear pump cited initially, the helical tooth set of thegears is configured such that, when viewed along a surface line of thegears, at least two tooth tip/root contact points of the meshing gearsare present; and the contour of the tooth spaces of the one gear ismatched to the teeth of the other gear in such a way that when a toothhas completely penetrated into the tooth space, its tooth tip almostcompletely fills up the tooth space radially inside the pitch circle.

The fact that at least two tooth tip/root contact points of the meshinggears are present along a surface line ensures precise concentricity ofthe meshing gears without wedging forces. The driven gear is in meshingengagement, continuously and in exact alignment, with the undrivennon-journal-mounted gear. This eliminates the risk that the undrivengear will come into contact with edges or corners of the overlappingcylindrical housing bores. Coordination of the contours of the toothspaces and teeth, in such a way that a tooth that has penetratedcompletely into the tooth space almost completely fills up the latter,on the one hand ensures that only an extremely small cavity volume, i.e.almost no volume at all, is present between the tooth space and toothand is filled with liquid, and thus only extremely small quantities ofliquid can be transported back at all, so that pump output efficiency ismaintained at high rotation speeds. If greater quantities weretransported back at high rotation speeds, pump output efficiency wouldbe greatly reduced. In addition, this configuration creates outstandingsealing between the delivery and intake sides of the pump.

As a result of the helical tooth set in conjunction with the two-pointcontact and the particular configuration of the tooth and tooth space,the flow conduit which is necessarily present between the meshing teethis sealed in such a way that any out-flow through it is efficientlyprevented.

It is possible with this special configuration, in the case of meshinggears having a helical tooth set, to dispense with a central journalbearing arrangement for the two gears. The axial bearing points in theconveying chambers which receive the gears are accordingly also omitted.The result is not only to eliminate numerous niches for bacteria, whichare difficult to clean and disinfect, but assembly and disassembly arealso very simple, since for assembly the gears simply need to be placedinto the conveying chamber, with no need to ensure that pivot bearingjournals are inserted into a specific bearing point. The special helicaltooth set not only results in very quiet-running gears, so that theoperator is not disturbed by loud pump noises, but leads to consistentlyexact meshing engagement with the drive gear. The two gears arereceived, with a slight radial clearance, in approximately cylindricaloverlapping openings. The diameter of the cylindrical openings is thusslightly greater than the diameter of the addendum circle of therespective gears. When the pump according to the invention is thenoperated with the non-journal-mounted gears, the relative overpressureon the delivery side causes the undriven gear to be displaced somewhattoward the intake side. In other words, during operation, the gears moveslightly out of coaxial alignment in the approximately cylindricalchamber in which the respective gear is received. The result of this,when considering the addendum circle of the undriven gear, is anapproximately half-sickle-shaped region, widening toward the deliveryside, between the addendum circle and the circular inner wall of theconveying chamber in which that gear is received.

This region on the one hand ensures that transfer of the conveyed liquidof a tooth space from the intake pressure state to the outlet pressureis accomplished extremely smoothly, especially in conjunction with thehelical tooth set and the configuration of the teeth, resulting not onlyin extremely quiet conveying but also in a transition from the toothspace to the pressure level with no loss of pressure. The combination ofsickle and helical tooth set yields particularly harmonious, smooth, andthus also quiet conveying.

Because of the sickle-shaped region opening toward the delivery side, aforce component is created which pushes the undriven gear toward thedriven gear. This movement of the meshing gears toward one anotherresults, in combination with the particular configuration of the teeth,in outstanding sealing between these gears, so that a self-sealingeffect can be achieved. Backflow from the teeth as they come out ofengagement, which impairs pump efficiency, is thereby greatly minimized.This is because the meshing teeth come out of engagement in a directionopposite to the inlet; i.e. quantities of liquid caught between thetooth space and tooth would be conveyed against the conveying direction,which can greatly impair pump output efficiency.

In production engineering terms, this has the considerable advantagethat there is no need to produce highly precise parts to tighttolerances, but rather that a relatively wide tolerance range isavailable so that economical production methods are possible. This alsoopens up the possibility, for example, of manufacturing the gears fromplastic materials, and optionally providing them for one-time use.

The good sealing attained by way of the working principle of theinvention, and less by way of high precision in parts production, alsoresults in a correlation between the pressure/flow characteristicsdiagram, the torque/speed characteristics field, and the current/voltagecharacteristics diagram that is more reproducible than with usual gearpumps. This allows these characteristics diagrams to be determined onceon one production unit; these matrix values can then be used forpressure and flow control, eliminating direct outlet pressuremeasurement (which is associated with a certain complexity).

In a further embodiment of the invention, a pump body is provided whichis detachably joined to a drive body, the inlet, cylindrical openingswith gears, and outlet being arranged in the pump body.

This feature has the considerable advantage that for cleaning anddisinfection, the pump body is removed from the drive body and thecomponents which come into contact with medical liquids, i.e. the inlet,conveying chambers, gears, and outlet, are present in one and the samecomponent, namely in the pump body, which can then be correspondinglycleaned and disinfected.

In a further embodiment of the invention, the pump body is configured sothat it can be placed onto the drive body.

This feature has the advantage that handling during disassembly andassembly is particularly simple, i.e. for example, after being used thepump body simply needs to be removed from the drive body, which is veryeasy and can be performed by even untrained persons.

In a further embodiment of the invention, the pump body is joinable tothe drive body via a bayonet coupling.

This feature has the advantage that a bayonet coupling is very easy toclose and open, and at the same time ensures the appropriate sealingcontact pressure between pump body and drive body.

In a further embodiment of the invention, the pump housing is configuredas a solid plastic part in which the cylindrical openings are recessedin such a way that the gears can be inserted into the cylindricalopenings from one side of the pump housing.

This feature has the considerable advantage not only that the pumphousing can be manufactured as an economical part, for example aninjection-molded part, but also that installation of the gears in thepump housing is very easy: they simply need to be pushed in or out oncethe pump cover has been pulled off. The plastic part can be manufacturedas a mass-produced item, so that it can be configured as a disposablepart, i.e. the pump body is discarded after a single use, and a new pumpbody is simply placed onto the drive body.

In a further embodiment of the invention, there projects from the drivengear a coupling stem which is insertable into a corresponding couplingcounterelement of a motor in the drive body.

This feature has the advantage that the nonpositive connection betweenthe drive mechanism and the driven gear can be created very easily byway of the push-in coupling.

In a further embodiment of the invention, an intermediate pin isarranged between the coupling stem and motor.

This feature has the advantage that the gear, with its drive stem, canbe easily removed and replaced by removing the pump cover, for examplevia a bayonet coupling. Because of its replaceability, the intermediatepin with its double-articulated effect also has the advantage thatdifferent coupling diameters can be used for single-use and multiple-usepump versions. This makes it possible to injection-mold the drive stemalong with the gear as a unit for the single-use version, and for themultiple-use versions to anchor into the driven gear a stainless,hardened, and sufficiently strong steel stem with a small outsidediameter. A small outside stem diameter results in a lowercircumferential speed at the corresponding sealing lip, and this in turnresults in less wear on the stem seal.

In a further embodiment of the invention, the coupling between thecoupling stem and motor is configured as a slot coupling.

This feature has the advantage that the coupling is self-aligning, i.e.regardless of the relative rotational position of the coupling stem andcoupling counterelement, alignment is accomplished and any shaft offsetis compensated for.

Thus by simply placing the pump body onto the drive body, the couplingbetween motor and driven gear can simultaneously also be aligned andclosed.

In a further embodiment of the invention, a stoppage sealing valve isarranged in the outlet.

This feature has the advantage that when the pump is stopped, nobackflow can occur in either direction. If the pump is being used, forexample, as an irrigation pump, it is usually conveying from a reservoirvessel located higher up, so that it is then possible to ensure inparticular that no backflow or over-flow can occur through the pump.

In a further embodiment of the invention, the stoppage sealing valve isconfigured as a ball-type nonreturn valve.

This feature has the advantage that the outlet can be blocked to preventbackflow or outflow during a stoppage using only a few components, forexample a spring-loaded ball, components which can easily be assembled,disassembled, and cleaned.

In a further embodiment of the invention, the stoppage sealing valve isconfigured as a slit body made of flexible material that is arranged inthe cross section of the outlet.

A passive stoppage sealing valve of this kind can be configured, forexample, by way of a simple cross-slit silicone disk. The outsidediameter of the slit disk corresponds to the outside diameter of a pumpoutlet tube. The diameter of the peripheral circle of the crossed slitsin the disk corresponds to the inside diameter of the pump outlet tube.The disk is simply held immovably between the end surface of the pumpoutlet tube introduced into the housing outlet bore and the inner stopsurface of the housing outlet bore. The differential pressure for thetransition from stoppage sealing to flow can be adjusted by way of thedisk thickness and/or the Shore hardness of the silicone disk.

In a further embodiment of the invention, the stoppage sealing valve isconfigured as a magnetically driven plunger, connected in parallel witha motor of the drive mechanism, which can be extended in blockingfashion into the cross section of the outlet when the motor switchesoff.

The advantage of this function is that an active stoppage shut-off valveis created. A flat plunger, not belonging externally to the replaceablepump body, acts, through a matching slot of the pump housing in theregion of the housing outlet bore, on a relatively thin-walled siliconetube introduced there. In one linear end position of the plunger theflow is sealedly shut off; in the other linear end position the fullflow is possible without a pressure loss. The housing slot and thenonrotatable plunger edge are configured so that regardless of thelinear stroke position of the edge, the pump body can unimpededly be putin place or removed with a quarter-turn in bayonet fashion. The outsidediameter of the thin-walled tube is somewhat larger than the diameter ofthe housing outlet bore. It is inserted via vacuum finger, andthereafter is sealed without adhesive bonding in all operating states ofthe housing bore.

In a further embodiment of the invention, an overpressure valve isprovided which, in the event of overpressure, moves a pump coverrelative to the pump housing in such a way that even though the drivemechanism is running, what occurs is not conveyance but rather backflowto the inlet.

This feature has the advantage that overpressure situations can beregulated with relative simple measures. In an overpressure situation,the pump cover is moved so as to create an opening from the outlettoward the inlet, so that the pump conveys back toward the inlet incirculating fashion.

In a further embodiment of the invention, an overpressure valve springwith plunger is provided in the drive body, and in an overpressuresituation allows the pump cover to tilt away from the pump housing onone side.

These features are particularly easy to manufacture in terms ofproduction engineering, for example by way of corresponding molded-onelements if the pump cover is configured as a plastic part. In anoverpressure situation the pump cover can then tilt slightly to theside, for example via a molded-on tilting edge, so that the seal of theconveying chamber between inlet and outlet is broken and the pumpconveys from the inlet through the resulting opening back toward theinlet. When the overpressure situation no longer exists, the plungerpushes the pump cover back again and the seal once again exists, so thatthe pump then conveys from the intake side to the delivery side.

In a further embodiment of the invention, there is received in the drivebody a pressure sensor which communicates with the outlet via a membraneand a stub line.

This feature has the advantage that the components which may bemechanically somewhat more complex, such as the pressure sensor, can bereceived in the drive body in a manner hermetically sealed off withrespect to the pump body, and thus do not need to be disassembled,cleaned, and sterilized after use. Technically complex pressuremonitoring and overpressure control systems can thus also be providedwithout impairing the simple configuration of the actual pump body, withthe advantages described previously.

In a further embodiment of the invention, the helical tooth set isconfigured as a herringbone tooth set.

This feature has the advantage that the herringbone tooth set can createa particularly intensive engagement at multiple points on the meshinggears, and the herringbone arrangement makes possible particularly goodsealing between the gears and compensates for axial forces.

It is understood that the features mentioned above and those yet to beexplained below can be used not only in the respective combinationsindicated, but also in other combinations or in isolation, withoutleaving the context of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained and described in more detail below withreference to preferred embodiments in conjunction with the accompanyingdrawings, in which:

FIG. 1 shows a longitudinal section of a medical gear pump that ismounted on a motor;

FIG. 2 shows a section along line II—II in FIG. 1;

FIG. 3 shows a partial and greatly enlarged view of the central regionof the section in FIG. 2;

FIG. 4 shows a side view of the two meshing gears;

FIG. 5 shows a perspective oblique view of the two meshing gears;

FIG. 6 shows a section along line VI—VI in FIG. 5;

FIG. 7 shows a greatly enlarged partial cross-sectional representationof the two meshing gears;

FIG. 8 shows a side view of the pump in a state rotated 90 degrees ascompared with the sectioned representation of FIG. 1;

FIG. 9 shows a plan view of the pump during an assembly step after apump body has been placed onto a drive body and before a bayonet guidehas been closed;

FIG. 10 shows a plan view of the pump after the bayonet closure has beenclosed; and

FIG. 11 shows a representation, comparable to the sectionedrepresentation of FIG. 2, of a further exemplary embodiment with anoverpressure valve embodiment;

FIG. 12 shows a partial section, comparable to the representation ofFIG. 1, along line XII—XII in FIG. 11, showing essentially the sectionthrough the drive body; and

FIG. 13 shows a partial representation of the section of FIG. 12 in anoverpressure situation.

FIG. 14 shows a partial section, comparable to the representation ofFIG. 1, of a further exemplary embodiment with an intermediate pinbetween the coupling stem and motor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A gear pump shown in FIGS. 1 through 10 is designated in its entiretywith the reference number 10.

Pump 10 comprises two essential constituents, namely a pump body 12 anda drive body 14.

FIG. 1 shows that drive body 14 of pump 10 is joined to a motor 15.

Pump body 12 substantially comprises a pump housing 16, a pump cover 54closing off the latter on one side, and gears 42 and 44 received in thepump housing. Projecting from pump housing 16, on its side facing drivebody 14, are bayonet flanges 18, 18′ and a bayonet stop 21.

Bayonet flanges 18, 18′ serve to engage into corresponding bayonetguides 20, 20′ on drive body 14.

Pump body 12 can thus be joined via a bayonet coupling to drive body 14.

This operation is shown in the sequence of FIGS. 9 and 10.

It is evident from the plan view of FIG. 9 that the approximatelycylindrical pump body 12 can be placed on drive body 14, which has aslightly greater diameter, in such a way that bayonet flanges 18 areaxially inserted into bayonet guides 20.

The bayonet coupling is then closed by rotation (clockwise in theexemplifying embodiment shown) approximately 45 degrees along arrow 91;the final assembled state is shown in FIG. 10, and corresponds to thesection shown in FIG. 1.

The simple, quick 45-degree bayonet assembly and disassembly process ofthe complete pump body 12 also allows for rapid emergency decoupling ordeactivation of pump 10 in this fashion, without spilling liquid ornegatively affecting the user or the device.

As is evident from FIG. 1, motor shaft 22, which is joined on the sidefacing pump body 12 to a slot coupling 26, is received centeredly indrive body 14.

Projecting from the approximately cylindrical pump housing 16, as isevident in particular from FIG. 1 and FIGS. 8 through 10, are twotubular fittings 28 and 30 running parallel to one another.

Tubular fitting 28 and its centeredly continuous cylindrical bore serveas inlet 32, which opens into a chamber 34.

Chamber 34 is configured as a centered gap 36, open toward the bottomside of pump body 12 that faces drive body 14.

Provided centeredly in gap 36 are two cylindrical openings 38 and 40,also opening toward the bottom side, which serve to receive gears 42 and44. A center point 48 of cylindrical opening 38 in which gear 42 isreceived also corresponds to the center point of the approximatelycylindrical pump housing 16 and of pump cover 54, as is evident fromFIGS. 9 and 10.

At the end located opposite inlet 32, gap 36 opens into an outlet 46which is configured as a centered continuous bore through tubularfitting 30.

Gear 42 is equipped with a pivot stem which protrudes axially at one endof gear 42 and is configured there as coupling stem 50. One end ofcoupling stem 50 is flattened and pointed to define an intermediate pin52. The pivot stem and gear 42 can be of one-piece or two-piececonfiguration.

As is evident in particular from the sectioned representation of FIG. 1,pump housing 16 comprises a pump cover 54 which is sealed with respectto pump housing 16 via an outer sealing ring 56. A further seal 58surrounds coupling stem 50 of gear 42 which extends through pump cover54.

Coupling stem 50 and thus gear 42 is guided sealingly but rotatably bypump cover 54. Intermediate pin 52 engages into a slot coupling 26 ofoutput shaft 22 of motor 15, thus creating a nonpositive connection.Gear 42 is therefore the driven gear. The other gear 44 is alsonon-journal-mounted. Both gears are guided in floating fashion incylindrical openings 38 and 40.

It is evident from the representations of FIGS. 4 through 6 that themeshing gears 42 and 44 are each equipped with a helical tooth set.

It is evident from FIGS. 4 and 6 that, when viewed along a surface line67, at least two tooth tip/root contact points 68 and 70 are present. Inother words, at least two successive tooth/gap pairs are in meshingengagement along a surface line. This makes possible exact guidance ofthe non-journal-mounted gear 44 via driven gear 42.

It is evident from the sectioned representation of FIG. 7 that thecross-sectional profile of a tooth 64 is such that tooth 64, when it haspenetrated completely into a having a tooth root 67, almost completelyfills it up in the region of its tooth tip 72, specifically in theregion radially inside pitch circle 76. The configuration of the toothflanks is such that upon meshing, a tip/root contact with nonpositiveengagement but without wedging effect is achieved. The remaining openspaces 78 and 79 are very small, just sufficient to allowrolling-contact motion. It is also evident from the sectionedrepresentation of FIG. 7 that only insignificant quantities of liquidcan thus be received in spaces 78 and 79.

It is evident from the sectioned representation of FIG. 3 that theundriven gear 44 rotates clockwise, and the driven gear 42counterclockwise.

As indicated by an arrow, liquid coming from inlet 32 is conveyed viathe radial outer side of gears 42 and 44 toward outlet 46.

It is apparent from the enlarged sectional representation of FIG. 7 thatonly extremely small quantities of liquid can be conveyed at all backtoward the inlet, so that backflow is negligibly low, thus considerablyincreasing efficiency and thus capacity. The leakage cross section is infact approximately 1% of the conveying cross section of a tooth space.

It is also evident from the enlarged representation of FIG. 3 thatduring operation, because of tolerances the non-journal-mounted gears 44and 42 move slightly in the direction of the inlet, specifically becauseof the pressure difference between inlet 32 and outlet 46. If addendumcircle 82 of gear 44 as shown in FIG. 3 by a dashed line is nowconsidered, it is evident that a sickle-shaped region 83, widening onthe delivery side toward outlet 46, has been created in the region ofthe upper (in the representation of FIG. 3) half between the inner sideof cylindrical opening 40 and addendum circle 82. This results in forcecomponents which press the two gears 44, 42 toward one another, so thatthe effect shown in FIG. 6 is even further enhanced.

As is evident in particular from the representations of FIG. 2 and FIG.3, a stoppage sealing valve 84 is arranged in outlet 46.

Stoppage sealing valve 84 comprises a ball-type non-return valve havinga ball 86, acted upon by the force of a spring 88, that is pressed byspring 88 onto a valve seat 89. The force of spring 88 is adjusted sothat during operation, ball 86 lifts off from valve seat 89, so thatliquid can be conveyed through outlet 46. In a backflow and stoppagesituation, ball 86 is pressed against valve seat 89 and seals outlet 46,so no conveyed volume can flow back or out through pump 10.

After pump 10 has been used, pump housing 16 can be rotated inaccordance with the sequence of FIG. 10 to FIG. 9, thus undoing thebayonet coupling, and pump housing 16 can be removed from drive body 14.In the process, coupling stem 50 automatically detaches from slotcoupling 26 of motor shaft 22 of motor 15. Once pump housing 16 has beenremoved and after pump cover 54 has been pulled out, gears 42 and 44 canbe taken out of the housing through the open side, and the individualparts can be cleaned and then sterilized; the simple geometricalconfiguration of slot 36 and inlet 32 and outlet 46 favors theseactions.

After sterilization, all that is necessary is to push gears 42 and 44back into cylindrical openings 38 and 40, insert pump cover 54, andplace pump body 12 back onto drive body 14 as shown in FIG. 9, and closethe bayonet coupling.

In an embodiment, provision is made for both gears 42 and 44 to beembodied as plastic gears, thus as single-use disposable parts, so thatonly the actual pump housing 16 and cover 54 need to be cleaned andsterilized.

In a further embodiment, pump housing 16 and pump cover 54 are alsoconfigured as disposable parts, so that no sterilization or cleaningoperations at all needs to be performed after use.

FIGS. 11 through 13 depict a variant of pump 10 in which an overpressurevalve arrangement 106 is provided in drive body 94.

A stub line 98 leads through cover 96 from the outlet of pump housing16. Stub line 98 stands on a membrane arrangement of two membranes 100,102.

Membrane 102 is a constituent of a pressure sensor 104.

Pressure sensor 104 thus senses the pressure present in the outlet, andcan thus detect an overpressure situation.

Pressure sensor 104 is coupled to overpressure valve 106.

Overpressure valve 106 has a plunger 108 that acts, via a spring 110 ona side diametrically opposite stub line 98, on cover 96, as alsoindicated in FIG. 11.

The pressure limitation can be adjusted via an adjusting screw 112. Asis evident from the representation of FIG. 11, cover 96 can be tilted,via a tilting edge 114, slightly away from the underside of the pumphousing and toward drive body 94, as is evident from the image sequencefrom FIG. 12 to FIG. 13.

FIG. 12 shows the normal situation, i.e. spring 110 presses cover 96,via plunger 108, against the open side of pump housing 16.

As is evident from FIG. 11, sealing surfaces 117, 118, 119, and 120,which represent a sufficient seal between the delivery and intake sides,are provided. The remaining surface is recessed approximately 0.5 mm,and is acted upon by outlet pressure.

In an overpressure situation, cover 96 tilts about tilting edge 114 andthereby presses plunger 108 against the force of spring 110, as shown inFIG. 13 by an arrow 109.

A connection is thus created between inlet and outlet, so that the pumpthen conveys from the inlet via gap 115 back toward the inlet.

FIG. 14 depicts another variant pf pump 10 in which an intermediate pin200 is arranged between the coupling stem 50 and motor 15.

Therefore, what is claimed, is:
 1. A medical gear pump for suction andirrigation comprising: a pump housing having an inlet and an outlet andtwo cylindrical openings therebetween; two meshing gears as conveyingelements, one of which gears is joined to a drive mechanism, said gearsbeing received in a non-journal-mounted fashion in the cylindricalopenings of said pump housing, each of said gears comprising a pluralityof helical teeth, each tooth having a tooth tip and a tooth root andforming a single continuous helix; wherein the teeth of each of saidgears mesh to define a helical tooth set which, when viewed along asurface line of said gears, defines at least two tooth tip/root contactpoints of said meshing gears, and wherein when a tooth of a first ofsaid gears has completely penetrated into a tooth space of a second ofsaid gears, its tooth tip substantially completely fills up said toothspace radially inside a pitch circle of the second of said gears; andwherein said pump housing and said gears define a path for liquid flowfrom the inlet, radially about the gears between the gears and the pumphousing, and to the outlet.
 2. The medical gear pump of claim 1, whereinsaid inlet, said cylindrical openings with said gears, and said outlettogether define a pump body, and wherein the pump body is detachablyjoined to a drive body.
 3. The medical gear pump of claim 2, whereinsaid pump body is adapted to be placed onto said drive body.
 4. Themedical gear pump of claim 3, wherein said pump body is joinable to saiddrive body via a bayonet coupling.
 5. The medical gear pump of claim 4,wherein said pump body is configured as a solid plastic part in whichsaid cylindrical openings are recessed whereby said gears are insertedinto said cylindrical opening from one side of said pump body.
 6. Themedical gear pump of claim 5, wherein a coupling stem projects from saiddriven gear which stem is insertable into a corresponding couplingcounterelement of a motor in said drive body.
 7. The medical gear pumpof claim 6, wherein an intermediate pin is arranged between saidcoupling stem of said driven gear and said motor.
 8. The medical gearpump of claim 7, wherein said coupling between said coupling stem andsaid motor is configured as a slot coupling.
 9. The medical gear pump ofclaim 1, wherein a stoppage sealing valve is arranged in said outlet.10. The medical gear pump of claim 9, wherein said stoppage sealingvalve is configured as a ball-type non-return valve.
 11. The medicalgear pump of claim 1, wherein said stoppage sealing valve is arranged insaid outlet and said stoppage sealing valve is configured as a slit bodymade of a flexible material that is arranged in a cross section of saidoutlet.
 12. The medical gear pump of claim 1, wherein a stoppage sealingvalve is arranged in said outlet, wherein said stoppage sealing valve isconfigured as a magnetically driven plunger, connected in parallel witha motor of a drive mechanism, which can be extended in a blockingfashion into a cross section of said outlet when said motor switchedoff.
 13. The medical gear pump of claim 1, wherein a pump body isprovided which is detachably joined to said drive body, said inlet, saidcylindrical openings with said gears and said outlet being arranged insaid pump body, and, further comprising an overpressure valve for movinga cover relative to said pump housing and to said drive body during anoverpressure situation in such a way that even though the drivemechanism is running, what occurs is not conveyance but rather returnflow to said inlet.
 14. The medical gear pump of claim 13, wherein saidoverpressure valve comprises an overpressure valve spring with plungerfor slightly tilting said pump cover laterally away from said pumphousing on one side during an overpressure situation.
 15. The medicalgear pump of claim 14, further comprising a pressure sensor disposed insaid drive body, which pressure sensor communicates with said outlet viaa membrane and a stub line.
 16. The medical gear pump of claim 1,wherein said helical tooth of the gears is configured as a herringbonetooth set.
 17. A medical gear pump for suction and irrigationcomprising: a pump housing having an inlet and an outlet and twocylindrical openings therebetween; two meshing gears as conveyingelements, one of which gears is joined to a drive mechanism, said gearsbeing received in a non-journal-mounted fashion in the cylindricalopenings of said pump housing, each of said gears comprising a pluralityof helical teeth, each tooth having a tooth tip and a tooth root;wherein the teeth of each of said gears mesh to define a helical toothset which, when viewed along a surface line of said gears, defines atleast two tooth tip/root contact points of said meshing gears, andwherein when a tooth of a first of said gears has completely penetratedinto a tooth space of a second of said gears, its tooth tipsubstantially completely fills up said tooth space radially inside apitch circle of the second of said gears; wherein said pump housing andsaid gears define a path for liquid flow from the inlet, radially aboutthe gears between the gears and the pump housing, and to the outlet; andwherein said inlet, said cylindrical openings with said gears, and saidoutlet together define a pump body, wherein the pump body is detachablyjoined to a drive body, and wherein said pump body is adapted to beplaced onto said drive body.
 18. The medical gear pump of claim 17,wherein said pump body is joinable to said drive body via a bayonetcoupling.
 19. The medical gear pump of claim 18, wherein said pump bodyis configured as a solid plastic part in which said cylindrical openingsare recessed whereby said gears are inserted into said cylindricalopenings from one side of said pump body.
 20. The medical gear pump ofclaim 19, wherein a coupling stem projects from said driven gear whichstem is insertable into a corresponding coupling counterelement of amotor in said drive body.
 21. The medical gear pump of claim 20, whereinan intermediate pin is arranged between said coupling stem of saiddriven gear and said motor.
 22. The medical gear pump of claim 20,wherein said coupling between said coupling stem and said motor isconfigured as a slot coupling.
 23. The medical gear pump of claim 17,wherein a stoppage sealing valve is arranged in said outlet.
 24. Themedical gear pump of claim 23, wherein said stoppage sealing valve isconfigured as a ball-type non-return valve.
 25. The medical gear pump ofclaim 17, wherein said stoppage sealing valve is arranged in said outletand said stoppage sealing valve is configured as a slit body made of aflexible material that is arranged in a cross section of said outlet.26. The medical gear pump of claim 17, wherein a stoppage sealing valveis arranged in said outlet, wherein said stoppage sealing valve isconfigured as a magnetically driven plunger, connected in parallel witha motor of a drive mechanism, which can be extended in a blockingfashion into a cross section of said outlet when said motor switchedoff.
 27. The medical gear pump of claim 17, wherein a pump body isprovided which is detachably joined to said drive body, said inlet, saidcylindrical openings with said gears and said outlet being arranged insaid pump body, and, further comprising an overpressure valve for movinga cover relative to said pump housing and to said drive body during anoverpressure situation in such a way that even though the drivemechanism is running, what occurs is not conveyance but rather returnflow to said inlet.
 28. The medical gear pump of claim 27, wherein saidoverpressure valve comprises an overpressure valve spring with plungerfor slightly tilting said pump cover laterally away from said pumphousing on one side during an overpressure situation.
 29. The medicalgear pump of claim 28, further comprising a pressure sensor disposed insaid drive body, which pressure sensor communicates with said outlet viaa membrane and a stub line.
 30. The medical gear pump of claim 17,wherein said helical tooth of the gears is configured as a herringbonetooth set.